Messages in this thread Patch in this message | | | Date | Thu, 17 Jun 2004 16:38:26 -0700 | From | "Adam J. Richter" <> | Subject | Patch: 2.6.7/fs/dnotify.c - make dn_lock a regular spinlock |
| |
Hello Stephen,
In linux-2.6.7/fs/dnotify.c, the local varible dn_lock is declared as rw_lock_t, but the lock is only taken exclusively. So, let's "document" this fact, save a few bytes and save a few cycles by changing it to spinlock_t.
I have tried running the dnotify user level program on a multiprocessing kernel with this change, and it seems fine.
In the near future, I expect to try to eliminate dn_lock by using parent_inode->i_sem instead, as the kmem_cache_t in dnotify.c does not need to be protected by a separate lock. However, such a change would require changes to the callers into dnotify, which currently make conflicting assumptions about whether they should be holding parent_inode->i_sem, child_inode->i_sem or neither when they call dnotify_parent or inode_dnotify, so that will require modifying many of the places that call into dnotify. So, I'd like to integrate this minor change first.
If this patch looks acceptable to you, could you please tell the appropriate person to integrate it or advise me what to do if you want me to proceed some other way? I don't know if you submit your patches directly to Linus or through someone else, like Al Viro.
-- __ ______________ Adam J. Richter \ / adam@yggdrasil.com | g g d r a s i l --- linux-2.6.7/fs/dnotify.c 2004-06-15 22:19:09.000000000 -0700 +++ linux/fs/dnotify.c 2004-06-17 15:07:31.000000000 -0700 @@ -23,7 +23,7 @@ int dir_notify_enable = 1; -static rwlock_t dn_lock = RW_LOCK_UNLOCKED; +static spinlock_t dn_lock = SPIN_LOCK_UNLOCKED; static kmem_cache_t *dn_cache; static void redo_inode_mask(struct inode *inode) @@ -46,7 +46,7 @@ inode = filp->f_dentry->d_inode; if (!S_ISDIR(inode->i_mode)) return; - write_lock(&dn_lock); + spin_lock(&dn_lock); prev = &inode->i_dnotify; while ((dn = *prev) != NULL) { if ((dn->dn_owner == id) && (dn->dn_filp == filp)) { @@ -57,7 +57,7 @@ } prev = &dn->dn_next; } - write_unlock(&dn_lock); + spin_unlock(&dn_lock); } int fcntl_dirnotify(int fd, struct file *filp, unsigned long arg) @@ -81,7 +81,7 @@ dn = kmem_cache_alloc(dn_cache, SLAB_KERNEL); if (dn == NULL) return -ENOMEM; - write_lock(&dn_lock); + spin_lock(&dn_lock); prev = &inode->i_dnotify; while ((odn = *prev) != NULL) { if ((odn->dn_owner == id) && (odn->dn_filp == filp)) { @@ -105,7 +105,7 @@ dn->dn_next = inode->i_dnotify; inode->i_dnotify = dn; out: - write_unlock(&dn_lock); + spin_unlock(&dn_lock); return error; out_free: kmem_cache_free(dn_cache, dn); @@ -119,7 +119,7 @@ struct fown_struct * fown; int changed = 0; - write_lock(&dn_lock); + spin_lock(&dn_lock); prev = &inode->i_dnotify; while ((dn = *prev) != NULL) { if ((dn->dn_mask & event) == 0) { @@ -138,7 +138,7 @@ } if (changed) redo_inode_mask(inode); - write_unlock(&dn_lock); + spin_unlock(&dn_lock); } EXPORT_SYMBOL(__inode_dir_notify); | |